[SDTEST-116] Send event_created and event_finished metrics for internal telemetry

[anmarchenko]

What does this PR do?
Adds event_created and event_finished metrics. As this PR is already large, I will implement other metrics in subsequent PRs.

Also this PR:

• only enables telemetry with Datadog Agent for now as agentless mode is not released yet in gem datadog
• refactors domain model code
• introduces telemetry helpers and constants
• bumps datadog dependency to 2.2 as this is currently the oldest version with metrics support
• adds minor changes to dev setup: run bundle in docker without bundler version, replace docker-compose command with docker compose command

How to test the change?
Tested by running test suite with staging settings, see (DD only) dashboard here.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 99.41973% with 3 lines in your changes missing coverage. Please review.

Project coverage is 98.88%. Comparing base (03910f2) to head (afd50da).

Files	Patch %	Lines
spec/datadog/ci/test_visibility/component_spec.rb	92.00%	2 Missing ⚠️
lib/datadog/ci/test_visibility/component.rb	98.63%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #200      +/-   ##
==========================================
+ Coverage   98.86%   98.88%   +0.01%     
==========================================
  Files         235      242       +7     
  Lines       10477    10837     +360     
  Branches      481      489       +8     
==========================================
+ Hits        10358    10716     +358     
- Misses        119      121       +2     

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